NORTHAMPTON COMMUNITY COLLEGE LEARNING CENTER
OPERATION OF SINGED NUMBERS
CONCEPTS
EXAMPLES
Addition of Two Signed Numbers
If the signs are the same,
add the values and keep the sign.
If the signs are different,
find the difference and
keep the sign of the larger number.
3 4 7
3  (4)  -7
3  4  1
3  (4)  -1
Subtracting Signed Numbers
x - y = x + (-y)
1. Change the subtraction symbol to addition
2. Change the sign of the second number
3. Add, as in previous section
3  4  3  (4)  -1
3  4  3  (4)  -7
3  (4)  3  (4)  1
3  (4)  3  (4)  7
Multiplication and Division
Same Signs → Answer is positive
Different Signs → Answer is negative
3  4  12
(3)  (4)  12
(3)  4  -12
3  (4)  -12
  
12
4
3
12
4
3
  
  
  
12
 -4
3
12
 -4
3
Other Tips
Double Negative
-  -a  = +a
3  (4)  3  4  7
Division by 0 is undefined
5 is undefined
0
0 divided by a nonzero number equals 0
0
0
5
Practice using your calculators if allowed
College Center Suite 315
610/861-5517
Spring 2011
Additions:
1)
5 + (-8) =
2)
-5 + 8 =
3)
-5 + (-8) =
4)
5 + (8) =
5)
7 + (-7) =
6)
10 + (-23) =
Subtractions:
1)
5 – (–8) =
2)
–5 – 8 =
3)
–5 – (–8) =
4)
5 – (+8) =
5)
9 – (+11) =
6)
–10 – (–15) =
7)
–4 – (–4) =
8)
–12 – (–4) =
9)
17 – (+19) =
Multiplications and Divisions:
1)
3 ∙ (-5) =
2)
(-3) ∙ 5 =
3)
(-3) ∙ (-5) =
4)
(-5) ∙ (-5) =
5)
(-11) ∙ 0 =
6)
(-16) ÷ 4 =
7)
(-9) ÷ (-3) =
8)
8 ÷ (-2) =
9)
40 ÷ (-5) =
Answers:
Additions: 1) -3 , 2) 3, 3) -13, 4) 13, 5) 0, 6) -13
Subtractions: 1) 13 , 2) -13, 3) 3, 4) 3, 5) 2, 6) 5, 7) 0, 8) -8, 9) -2
Multiplications/Divisions:
1) -15 , 2) -15, 3) 15, 4) 25, 5) 6, 6) -4, 7) 3, 8) -4, 9) -8